"From across (some region)" means "from one side of the region to the other", which figuratively does mean "from every part of the region".
Since it's not specifically mentioned there is no reason to think that all the artisans collaborated on a single piece. Here "work" is an uncountable (or mass) noun meaning artwork -- all of the individual pieces by all of the artisans. Example:
This month the museum will feature work by various Impressionist painters.
Side note: There is a difference between an artist and an artisan. While there is often some element of artistry in what artisans do, an artisan is someone proficient in a trade, who generally makes items that have both practical and aesthetic value.
For example, a particularly skilled cheesemaker could be called both an artisan, and an artist with cheese. The cheese has practical value in that it can be eaten, but how the cheesemaker selects and combines ingredients can be considered an art.